Use of a disulfide/dithiol compound in a seal for anodized aluminum

ABSTRACT

Provided is a method for sealing an article with a non-chrome corrosion inhibitor seal. The method may include applying an aqueous-based suspension comprising a thiol-containing corrosion inhibitor on a surface of an anodized substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. patent application Ser. No.14/851,888 filed Sep. 11, 2015, which claims priority benefit of U.S.Provisional Patent Application Ser. No. 62/121,618, filed on Feb. 27,2015, the entireties of which are incorporated herein by reference.

FIELD

Disclosed herein are non-chrome corrosion inhibiting compositions andmethods of using the non-chrome corrosion inhibiting compositions as aseal for corrosion control of metals.

BACKGROUND

Corrosion is defined as the chemical or electrochemical reaction betweena material, usually a metal, and its environment that produces adeterioration of the material and its properties. Corrosive attackbegins on the surface of the metal. The corrosion process involves twochemical changes. The metal that is attacked or oxidized undergoes ananodic change, with the corrosive agent being reduced and undergoing acathodic change. The tendency of most metals to corrode creates a majormaintenance challenge for metals and metal products, particularly inareas where adverse environmental or weather conditions exist.

Corrosion of aluminum is a major problem for the aerospace and manyother industries. One current technique to mitigate this probleminvolves anodization of the aluminum followed by an immersion seal.Typically, this seal involves the use of hexavalent chrome, which isincreasingly regulated. Chromium-based anti-corrosive systems containinghexavalent chromium compounds have proven to be an extremely useful andversatile group of chemistries that are extensively used in aircraftmetal treatment processes. They impart many beneficial anti-corrosivecharacteristics to metallic substrates on which they are applied andhave been used extensively for the pre-treatment of metals beforecoating, adhesive bonding, and surface finishing.

Concern about chromium—and in particular, hexavalent chromium—in theenvironment has generated a need to replace chromium-based systems.Therefore environmentally preferable, commercially acceptablealternatives to chromium-based systems are a welcome addition tocorrosion prevention coatings.

SUMMARY

Described herein is a method for sealing an article with a non-chromecorrosion inhibitor seal. The method includes applying an aqueous-basedsuspension comprising a thiol-containing corrosion inhibitor on asurface of an anodized substrate.

Also described herein is a method for preparing an aqueous-based,non-chrome corrosion inhibitor seal composition that includes adisulfide/dithiol compound. The method includes forming a mixture havinga thiol-containing corrosion inhibitor and water. The method alsoincludes agitating the mixture to form a suspension that includesnano-sized particles of the thiol-containing corrosion inhibitor.

Also described herein is an article. The article includes an anodizedsubstrate having an anodic oxide coating. The anodic oxide coatingincludes a plurality of cells, each of the plurality of cells definingat least one pore. The article also includes a non-chromecorrosion-inhibitor seal disposed on the substrate. The seal includesthiol-containing corrosion inhibitor particles. At least one of thethiol-containing corrosion inhibitor particles is disposed in the atleast one pore.

The particles, compositions and suspensions disclosed herein may be usedas seals for providing corrosion protection and durability for articlessuch as components of an airplane. Use of the particles, compositionsand suspensions and practice of the methods described herein may resultin cost savings and improved work conditions due to use of non-chromematerials. For example, use of the particles, compositions andsuspensions and practice of the methods described herein avoidsconventional sodium or potassium dichromate solution for corrosionprotection of anodized aluminum, reduces energy consumption; yet stillprovides equivalent corrosion protection performance as conventionalanodic seals.

Additional advantages will be set forth in part in the description whichfollows, and in part will be understood from the description, or may belearned by practice thereof. The advantages will be realized andattained by means of the elements and combinations particularly pointedout in the appended claims.

It is to be understood that the foregoing general description and thefollowing detailed description are exemplary and explanatory and are notrestrictive of that which is claimed.

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate examples and together with thedescription, serve to explain the principles of that which is describedherein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates one example of an aircraft.

FIG. 2 shows an example structure of an anodized substrate surface.

FIGS. 3A-3B illustrates an aqueous-based, non-chrome corrosion inhibitorseal composition applied to an anodized article; FIG. 3A is a close upview of a portion of FIG. 3B.

FIG. 4 is a flowchart depicting a method of making a corrosioninhibiting seal.

FIGS. 5A-5C are images of test panels used in a first example beforesalt spray exposure.

FIGS. 6A-6D are images of representative test panels used in a firstexample after 4 hours of neutral salt spray testing.

FIGS. 7A-7D are images of test panels used in another example beforesalt spray exposure.

FIGS. 8A-8D are images of representative test panels used in anotherexample after 336 hours of neutral salt spray testing.

DETAILED DESCRIPTION

Reference will now be made in detail to the present descriptions,examples of which are illustrated in the accompanying drawings. Whereverpossible, the same reference numbers will be used throughout thedrawings to refer to the same or like parts.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the descriptions are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value inherently contains certain errorsnecessarily resulting from variance found in their respective testingmeasurements. Moreover, all ranges disclosed herein are to be understoodto encompass sub-ranges subsumed therein. For example, a range of “lessthan 10” can include sub-ranges between (and including) the minimumvalue of zero and the maximum value of 10, that is, any and allsub-ranges having a minimum value of equal to or greater than zero and amaximum value of equal to or less than 10, e.g., 1 to 5. In certaincases, the numerical values as stated for the parameter can take onnegative values. In this case, the example value of range stated as“less that 10” can assume negative values, e.g. −1, −2, −3, −10, −20,−30, etc.

The following is described for illustrative purposes with reference tothe Figures. Those of skill in the art will appreciate the followingdescription is exemplary in nature, and that various modifications tothe parameters set forth herein could be made without departing from thescope of the present disclosure. It is intended that the specificationand examples be considered as examples. The various descriptions are notnecessarily mutually exclusive, as some descriptions can be combinedwith one or more other descriptions to form combined descriptions.

Described herein are compositions that may be used for coating aluminum,and aluminum alloys, among other metals, including for sealing anodizedaluminum and anodized aluminum alloys, among other metals. In anexample, a method includes applying a prepared 1 wt % suspension of 5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione) and deionized water onaluminum and aluminum alloys, including anodized aluminum and anodizedaluminum alloys, among other metals, at room temperature.

Articles, such as metal surfaces that are subject to environmentalcorrosion, in particular to oxidative corrosion, such as those of anaircraft shown in FIG. 1, can be protected against such corrosion. Ametal surface of such an article may be protected with a barrier oxidefilm that can be grown on certain metals, including, but not limited toaluminum, niobium, tantalum, titanium, tungsten, and zirconium, byanodizing the metal. Aluminum is unique among these metals in that, inaddition to the thin barrier oxide, anodizing aluminum alloys in certainacidic electrolytes produces a thick oxide coating, known as an anodicoxide, containing a high density of microscopic pores. By exposing theanodized coating to hot water for example, at a temperature betweenabout 190° F. to about 212° F., oxide on the surface and within thepores reacts to make a hydrous oxide that has a lower density than theanodic oxide. Because of its lower density, the hydrous oxide occupies agreater volume than the anodic oxide from which it formed. This reactionproduct fills the pores and makes an anodized layer that is stable undera wide range of atmospheric and environmental conditions. This processof closing the pores after growth of the oxide is called “sealing” andit improves corrosion resistance of the metal.

As shown in FIG. 2, a coating 101, such as a porous anodic oxidecoating, may be formed on a substrate 103, which may be aluminum or analuminum-alloy. Anodic coating 101 may be formed during an anodizingprocess, as described above, and may have a thickness of about 100 m.The porous coating 101 may have a cellular structure comprising aplurality of cells 118, which may be hexagonal. Each of the plurality ofcells 118 may define at least one of pores 122. For example, one ofpores 122 may be disposed within a respective one of the plurality ofcells 118 and may extend between an anodic barrier formed on substrate103 and a surface of the coating 101. The plurality of cells 118 mayinclude uniform, hexagonal cells. Some anodization conditions produceanodic coatings with more disorder, for example, a cellular structurehaving a distribution of cell size and pore diameter. Cell and poredimensions depend on anodizing bath composition, temperature, andvoltage, among other factors. The plurality of cells 118 may have adiameter in the range of from about 50 nm to about 300 nm, and the atleast one of pores 122 may have a diameter in the range of from about ⅓to about ½ of the cell diameter. The cell population density may be fromabout 10 per μm² to more than 100 per μm². The aspect ratio may be inthe order of 1000:1. For example, a coating 101 grown in sulfuric acidmay have a thickness of 20 to 50 μm and may have 20 nm pores.

In a method described herein, there is a method for applying anon-chrome corrosion inhibitor composition on an article. The non-chromecorrosion inhibitor composition may be a non-chrome corrosion inhibitorseal. The method can include sealing an article, for example, ananodized substrate. The method can include forming a non-chromecorrosion inhibitor seal on an anodized substrate. As used herein, theterm “non-chrome” refers to materials that are chromium free, forexample, they may not include chromium (VI). For example, as shown inFIGS. 3A-3B, a corrosion-inhibiting seal may be formed on a surface ofsubstrate 103 of article 100 as a suspension 105, and flows into pores122. The substrate 103 may be an anodized metal, such as anodizedaluminum or an anodized aluminum alloy. The surface of the substrate 103may be an anodic coating 101, such as an oxide, formed during ananodizing process. The corrosion-inhibiting seal may be an aqueous-basedsuspension that includes a corrosion-inhibitor in a carrier. Thecorrosion-inhibitor may be a non-chromium-based corrosion inhibitor, forexample, a thiol-containing corrosion inhibitor. The thiol-containingcorrosion-inhibitor may be at least one thiol-containingcorrosion-inhibitor particle 107, for example, a plurality ofthiol-containing corrosion-inhibitor particles. The carrier 109 may bewater.

As shown in FIG. 3A, which is a magnified view of a portion of FIG. 3B,the substrate 103 may be an anodized substrate and may include a coating101. In other words, a surface of the substrate 103 may be formed of ananodic coating. The anodic coating may include the characteristics ofthe coating 101 described with respect to FIG. 2 above. Thus, the anodiccoating may be an oxide coating having a structure that includes aplurality of cells 118, each of the plurality of cells 118 defining atleast one of pores 122. The at least one thiol-containingcorrosion-inhibitor particle 107 of the suspension 105 may be aplurality of thiol-containing particles. The at least onethiol-containing particle may have a particle diameter that is smallerthan a pore diameter of at least one of pores 122. Thus, at least onethiol-containing corrosion-inhibitor particle 107 of suspension 105 maybe transported into and disposed in at least one of pores 122 of theanodized substrate's anodic coating. Capillary pressure may provide adriving force that causes the at least one thiol-containingcorrosion-inhibitor particle 107 of suspension 105 to be transportedwith carrier 109 into one or more of pores 122. At least onethiol-containing corrosion-inhibitor particle 107, therefore, may bedisposed in a respective one of pore 122. Upon transporting at least onethiol-containing corrosion-inhibitor particle 107 into at least one ofpores 122, excess volume of suspension 105 may be removed from thesubstrate. The substrate may also be exposed to a rinse with either tapwater or de-ionized (DI) water. Although some of the carrier 109 may beremoved, such as via evaporative air-drying, from the surface, somevolume of carrier 109 may remain behind, such as disposed in some of thepores. In other words, although the substrate may be rinsed, some of thethiol-containing suspension may remain in the pores, or at least some ofthe thiol-containing corrosion-inhibitor particle may remain in thepores.

Unlike conventional seals which are deposited onto anodized substratesat temperatures between about 190° F. and about 212° F., in the methoddescribed herein, for example, with respect to forming a non-chromecorrosion inhibitor seal on article 100 in FIGS. 3A-3B, suspension 105may be applied on the substrate at a temperature in the range of fromabout room temperature (e.g., ambient temperature, which may be about68° F. to about 79° F., including about 73° F.) and about 212° F. Forexample the suspension may be at a temperature in the range of fromabout room temperature and about 212° F. when the suspension is appliedon the substrate. That is, the suspension 105 may be at room temperaturewhen it is applied on the substrate, for example, when the substrate isimmersed in the suspension, and the substrate may also be at roomtemperature.

As shown in FIG. 3A, at least one thiol-containing corrosion-inhibitorparticle 107 may have a diameter such that a plurality of the at leastone corrosion-inhibitor particle 107 are transported into and disposedin one or more of pore 122. Accordingly, the at least onethiol-containing corrosion-inhibitor particle 107, as described above,may be a nano-sized particle that is smaller than a pore diameter, thepore diameter being about ⅓ to about ½ of the cell diameter, and thecell diameter being in a range of from about 50 nm to about 300 nm.While not limited to any particular theory, it is believed that bytransporting the at least one thiol-containing corrosion-inhibitorparticle 107 into the pore, the particle prevents corrosion reactionsbetween the substrate and materials in the environment byelectrochemically reacting to resist corrosion.

The corrosion-inhibitor particles used in a non-chrome corrosioninhibitor seal may be derived from crude non-chrome corrosion inhibitorparticles, for example, bulk non-chrome corrosion inhibitor particlesformed according to known synthesis routes or available as commercialpowders. For example, FIG. 4 is a flow-chart that describes a method forpreparing an aqueous-based, non-chrome corrosion inhibitor sealcomposition. At 401, a corrosion inhibitor is provided, for example, inpowder form (although not limited to powder form). The corrosioninhibitor may be a disulfide/dithiol compound, for example, an insolublethiol or sulfide containing organic molecule. The thiol or sulfidecontaining organic molecule may be a polydisulfide, such as amercaptan-terminated polysulfide of dimercaptothiadiazole (DMcT). Forexample, the polydisulfide may be represented by formula I:

where n is 1 or 2, and polymers thereof.

Accordingly, the crude corrosion inhibitor may be5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione), available as VANLUBE®829 (Vanderbilt Chemicals, LLC, Norwalk, Conn.), which has a structurerepresented by formula II:

At 402, a carrier such as water is provided. The water may be de-ionized(DI) water. Other carriers capable of mixing with the corrosioninhibitor to form a suspension may be used. At 403, the water andcorrosion-inhibitor powder are combined to form a mixture. An exemplarymixture includes 0.2 wt % to 10 wt % of5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione) in water. Anotherexemplary mixture comprises a 1 wt % to 3 wt % suspension of5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione) in water. Anotherexemplary mixture comprises 1 wt % of5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione) in water. Otherdithiol-based corrosion inhibitors may be used, such as INHIBICOR™ 1000(available from WPC Technologies).

At 405, at least one particle, such as the at least one thiol-containingcorrosion-inhibitor particle 107 is formed by agitating the mixture,such as via mechanical agitation. The mixture may be agitated for asufficient time such that the crude corrosion inhibitor is formed intoat least one particle, and the at least one particle's diameter isreduced such that the particle is a nano-sized particle. While notlimited to any particular theory, it is believed that by agitating thecrude corrosion-inhibitor in water, the crude corrosion-inhibitor isreduced into particles that are small enough to remain in suspension.

At 407, the suspension may be applied onto a surface of a substrate, forexample, a surface of substrate 103, which may be an anodized substrateas described above. The suspension may be applied at a temperature inthe range of from about room temperature to about 212° F. Excess amountof suspension may be removed, such as by evaporating away the water viaair-drying, or via rinsing with tap or DI-water. Some of the water fromthe suspension may remain on the substrate, for example, in the pores ofan anodic coating of an anodized substrate. The particles of thesuspension may be reduced in size, for example, during step 405, suchthat at least one particle has a diameter that is smaller than adiameter of a pore. Accordingly, at least one particle may betransported into and disposed in at least one pore to seal the substrateas in step 409. The suspension may be applied to a substrate viaimmersion, for example, tank immersion, or by any appropriate method,such as dip coating, spin coating, spray coating, or brushing on.

In addition to the corrosion-inhibiting particle and water, suspensionformulations of the non-chrome, corrosion inhibiting seal can containother materials. For example, a colorant or and any other material thatadds useful properties to the seal, or at least does not reduce thefunctionality of the seal, can be included in the suspension in amountsthat are known to those of skill in the art of seals for anodic coatingsof anodized substrates.

It is believed that the present methods can be used to prevent or reducecorrosion for any corrodible metal. The methods and compositions areparticularly useful on aluminum alloys such as 2024-T3 aluminum.

EXAMPLES Example 1—Method of Making a Disulfide/Dithiol Compound

A 1 wt % composition of 5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione)was prepared from VANLUBE® 829 in deionized water. This composition wasprocessed on a paint shaker using glass beads to help incorporate theVANLUBE® into the water. A high speed shear mixer or a centrifugalplanetary mixer would work too. A majority of the VANLUBE® did notappear to dissolve, and a portion was reduced to nano-sized particleswhich stayed in suspension.

Example 2˜Use of a Disulfide/Dithiol Composition to Increase CorrosionResistance of Aluminum and its Alloys

Twelve (12) 2024-T3 aluminum panels (3″×6″×0.032″) were used as testspecimens.

Three of these panels were chromium conversion coated to use ascontrols.

Three panels were put through an aluminum cleaning processing line(solvent wipe, alkaline clean and deoxidized) prior to immersion in the1 wt % suspension of Example 1.

Immersion time was 5 minutes at room temperature. These panels were thenrinsed.

Three panels were wet abraded with Scotch-Brite 7447 pads, rinsed andallowed to dry.

The 1 wt % suspension of Example 1 was then spray applied to the panels.The panels were kept wet with the suspension for 2 minutes at roomtemperature. These panels were then allowed to air dry.

Three panels were solvent wiped for use as control panels.

FIGS. 5A-5C are images of test panels described above before salt sprayexposure. A chromium conversion coated panel is shown in FIG. 5A, apanel that was immersed in the 1 wt % suspension of Example 1 and rinsedis shown in FIG. 5B, and a panel on which the 1 wt % suspension fromExample 1 was spray-applied is shown in FIG. 5C. The use of adisulfide/dithiol compound (even in water), while not as effective ashexavalent chrome, improved the corrosion resistance of aluminum and itsalloys.

The panels were then placed into neutral salt spray per ASTM B-117 fortesting. After 4 hours of exposure the chromium-treated panels wereunaffected. The panels which had been abraded performed better than theimmersed and rinsed panels or the bare unprocessed panels.

FIGS. 6A-6D are images of representative test panels described aboveafter 4 hours of neutral salt spray testing described above. A chromiumconversion coated panel is shown in FIG. 6A, a panel that was immersedin the 1 wt % suspension of Example 1 and rinsed is shown in FIG. 6B, apanel on which the 1 wt % suspension from Example 1 was spray-applied isshown in FIG. 6C, and a bare unprocessed panel of 2024-T3 aluminum isshown in FIG. 6D.

Accordingly, it was observed that the use of a disulfide/dithiolcompound (even in water), while not as effective as hexavalent chrome,improved the corrosion resistance of aluminum and its alloys.

Example 3—Comparison Between 5 wt % Sodium Dichromate Compound and 1%Disulfide/Dithiol Compound as a Seal for Anodized Aluminum

Twelve (1) 2024-T3 aluminum panels (3″×6″×0.032″) were used as testspecimens. The test panels were anodized simultaneously in one batch.

Three of these panels were sealed in a hot (200° F.) 5% sodiumdichromate suspension for 5 minutes. Three of the panels were sealed inhot (200° F.) DI water for 5 minutes. Three of the panels were sealed inroom temperature 1 wt % suspension of Example 1 for 5 minutes. Three ofthe panels were sealed in hot (200° F.) 1 wt % suspension of Example 1for 5 minutes.

FIGS. 7A-7D are images of representative ones of the test panels beforesalt spray exposure. A panel that was sealed with the hot dichromatesuspension is shown in FIG. 7A, a panel that was sealed with hot DIwater is shown in FIG. 7B, a panel that was sealed with the roomtemperature 1 wt % suspension from Example 1 is shown in FIG. 7C, and apanel that was sealed with the hot 1 wt % suspension from Example 1 isshown in FIG. 7D.

The panels were then placed into neutral salt spray per ASTM B-117 fortesting. After 336 hours (2 weeks) of exposure, all of the panels wereunaffected.

FIGS. 8A-8D are images of representative ones of the test panels afterthe 336 hours of neutral salt spray testing. A chromium conversioncoated panel is shown in FIG. 8A, a panel that was immersed in hot DIwater is shown in FIG. 8B, a panel on which room temperature 1 wt %suspension from Example 1 was applied is shown in FIG. 8C, and a panelon which hot 1% suspension of Example 1 was applied is shown in FIG. 8D.

It was observed that the use of a disulfide/dithiol compound in water,as a seal for anodized aluminum meets the corrosion resistancespecification of 336 hours.

While the present teachings have been illustrated with respect to one ormore implementations, alterations and/or modifications may be made tothe illustrated examples without departing from the spirit and scope ofthe appended claims. For example, it will be appreciated that while theprocess is described as a series of acts or events, the presentteachings are not limited by the ordering of such acts or events. Someacts may occur in different orders and/or concurrently with other actsor events apart from those described herein. Also, not all processstages may be required to implement a methodology in accordance with oneor more aspects or descriptions of the present teachings. It will beappreciated that structural components and/or processing stages may beadded or existing structural components and/or processing stages may beremoved or modified.

Further, one or more of the acts depicted herein may be carried out inone or more separate acts and/or phases. Furthermore, to the extent thatthe terms “including,” “includes,” “having,” “has,” “with,” or variantsthereof are used in either the detailed description and the claims, suchterms are intended to be inclusive in a manner similar to the term“comprising.” The term “at least one of” is used to mean one or more ofthe listed items may be selected. Further, in the discussion and claimsherein, the term “on” used with respect to two materials, one “on” theother, means at least some contact between the materials, while “over”means the materials are in proximity, but possibly with one or moreadditional intervening materials such that contact is possible but notrequired. Neither “on” nor “over” implies any directionality as usedherein. The term “about” indicates that the value listed may be somewhataltered, as long as the alteration does not result in nonconformance ofthe process or structure to the illustrated descriptions. Finally,“exemplary” indicates the description is used as an example, rather thanimplying that it is an ideal.

Other implementations will be apparent to those skilled in the art fromconsideration of the specification and practice of what is describedherein. It is intended that the specification and examples be consideredas exemplary only, with a true scope and spirit of the implementationsbeing indicated by the following claims.

What is claimed is:
 1. An article, comprising: an anodized substratehaving a surface; and a seal comprising a thiol-containing corrosioninhibitor disposed on the surface of the anodized substrate.
 2. Thearticle of claim 1, wherein the surface of the anodized substratecomprises an anodic oxide coating.
 3. The article of claim 1, whereinthe thiol-containing corrosion inhibitor comprises thiol-containingcorrosion-inhibitor particles.
 4. The article of claim 3, wherein theanodic oxide coating comprises a plurality of cells, each of theplurality of cells defining at least one pore.
 5. The article of claim4, wherein at least one of the thiol-containing corrosion-inhibitorparticles has a particle diameter that is smaller than a pore diameterof the at least one pore.
 6. The article of claim 4, wherein each of theplurality of cells comprise a cell diameter in a range of from about 50nm to about 300 nm.
 7. The article of claim 4, wherein each of theplurality of cells comprises a cell diameter, and wherein the at leastone pore comprise a pore diameter that is about ⅓ to about ½ of the celldiameter.
 8. The article of claim 4, wherein at least one of thethiol-containing corrosion-inhibitor particles is disposed in the atleast one pore.
 9. The article of claim 3, wherein the thiol-containingparticles comprise 5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione. 10.The article of claim 3, wherein the thiol-containing particles comprisenano-sized particles.
 11. The article of claim 1, wherein the sealcomprises a non-chrome corrosion inhibitor seal.
 12. The article ofclaim 1, wherein the seal is formed by applying an aqueous-basedsuspension on the surface of the anodized substrate, wherein theaqueous-based suspension comprises the thiol-containing corrosioninhibitor.
 13. The article of claim 12, wherein a temperature of theaqueous-based suspension, when it is applied on the anodized substrate,is in the range of from about room temperature to about 212° F.
 14. Thearticle of claim 13, wherein the temperature is in the range of fromabout 68° F. to about 79° F.
 15. The article of claim 13, wherein theaqueous-based suspension comprises 0.2 wt % to 10 wt % of5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione) nano-sized particles inwater.
 16. The article of claim 15, wherein the aqueous-based suspensionconsists of 0.2 wt % to 3 wt % of the5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione) nano-sized particles inthe water.
 17. The article of claim 1, wherein the anodized substratecomprises anodized aluminum or an anodized aluminum alloy.
 18. Anarticle, comprising: an anodized substrate comprising an anodic oxidecoating, wherein the anodic oxide coating comprises a plurality ofcells, each of the plurality of cells defining at least one pore; and anon-chrome corrosion-inhibitor seal disposed on the substrate, whereinthe seal comprises thiol-containing corrosion inhibitor particles, andwherein at least one of the thiol-containing corrosion inhibitorparticles is disposed in the at least one pore.
 19. The article of claim18, wherein the thiol-containing corrosion inhibitor particles comprisenano-sized particles.
 20. The article of claim 19, wherein thenano-sized particles comprises5,5-dithiobis-(1,3,4-thiadiazole-2(3H)-thione).